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Common Problems Associated with Pad Printing
by Liam Clancy
In a perfect world, all pad printers would have their machine in a stable
environment, one where room temperature, ink to thinner mixing ratios, machine
cycle times, etc., are all controlled and kept consistent from one day to the
next. Machine operators that are trained today would still be operating those
same machines for years to come.
Unfortunately, with the exception of a few customers, this is rarely the case.
Too often, the pad printing process is considered a poor relation to other more
high profile processes, like injection molding or assembly operations, both of
which may very likely be a company’s main source of income. Few customers
appreciate the value that a printed logo, company name, or decoration brings to
the final product.
The most common problems associated with the pad printing process are as
1. Understanding the Process
Pad printing is not the ‘black art’ commonly referred to by those experiencing
application problems. In order to maintain the process, you need to have a basic
understanding of what actually takes place during the operation of any pad
printing machine. Your machine or consumable supplier can explain this process
2. Consumable Life
It is recommended to always ask for guidelines on the expected life of your
consumables. In most cases, the customer exceeds the expected lifespan in
production. This is completely understandable in that cost is always a major
factor. However, it should be understood that frequent changes of pads, clichés,
and ink are common and more often than not, necessary, to keep a crisp, quality
3. Ink and Pad Selection
Quite often a customer will struggle to identify an ink suitable for a
particular substrate, or a pad that will successfully transfer the image without
compromising its quality. If you are in any doubt, your pad printing supplier is
the best place to help you make these decisions. Often sample parts can be sent
to your consumable supplier where they can be tested and the results reported
back to you, usually at no charge.
4. Printing Un-treated Plastics
The wide use of polyethylene and polypropylene plastics, as well as their
copolymers and alloys, has increased greatly in recent years. As a result,
everyone using these plastics is searching for a printing ink that will not
require the added cost and hassle of pre-treating.
Polyolefins are very difficult to bond to based on their non-polar, non-porous
and chemically inert surfaces. Their high degree of chemical inertness to
solvents generally limits the usefulness of solvent bonding as a viable printing
technique. One successful approach to these materials involves proper surface
pretreatment prior to bonding. The pretreatments, which are widely accepted,
include chemical wiping, flame treatments, corona discharge and gas plasma.
On occasion, it is possible to find an ink that will stick to polyolefins
without any need for pretreatment; unfortunately this is more the exception than
the rule. This is likely to remain the case because many of today’s polyolefins
consist of reground materials that offer no consistency from one batch to the
next. The plastic properties remain but printing requirements drastically
Because so many factors are involved in the pad printing process, there may be
as many as two or three reasons that you are not achieving a quality print.
Having experience and knowledge of the process, as well as support from your
supplier are the only guaranteed ways to make your pad printing operation
successful. Hopefully the information and tables in this article will help with
many of the more common challenges you might experience, but establishing good
support from your machine and consumable suppliers is equally as important to
Problems and their
|Ink not being picked
up from the etch
|Ink is too thick
||This can occur at set-up
or during the process itself. Solvent evaporation occurs throughout
normal operation – add more thinner to the ink.
|Ink is too thin
||Your ink may be drying out in the etch
prior to the pad coming in contact with it. Increase the speed of your
machine. Mix a new batch of ink.
|Working with a new pad
||There may be a large
amount of silicone on the surface of your pad. Wipe the excess oil from
the pad using the same solvent used in your ink, remove any lint by
applying low tack pad cleaning tape.
|You may be using the wrong pad
||Speak to your supplier about correct
|Image not being
released from your pad
|Ink may have dried on pad
prior to application
||Speed up machine. Add
retarder to the ink – this slows down the solvent evaporation rate.
|Ink may be too wet
||Slow down your process. Thin out your ink.
|Printing surface may be
oily or un-clean
||Check your substrate for
|Pad may be too old
||Your pad needs a very thin layer of
silicone oil on its surface to help release the ink. Over time your
solvent based ink eats away at this silicone, the pad will appear dry.
It is then time to replace your pad.
|Image quality is poor
|All of the ink is not
transferring to your substrate
||Ink may be drying to fast
on pad. Pad may be at the end of its life.
|Insufficient downward pressure at ink
||Increase the vertical pressure on your pad
at ink pick up.
pressure at ink application
||Increase the vertical
pressure on your machine in the printing position.
|You may be using the wrong pad
||Speak to your supplier about correct
Poor ink adhesion
|You are using the wrong ink
||Have your supplier suggest an
|The print surface is oily or unclean
||Check your substrate for contaminants, clean if
necessary with alcohol, wait for part to dry before printing.
|Printing surface may require
||Get advice from your pad printing
supplier on the most suitable method of treating.
Plastics Decorating would like to thank Liam Clancy, Managing Director of
Teca-Print USA Corp. For further information he can be reached at (978) 667-8655
x 222 or at email@example.com.